1. Field of the Invention
The present invention relates to a radiation phase contrast imaging apparatus that employs a diffraction grating.
2. Description of the Related Art
An X-ray phase contrast imaging apparatus, which utilizes Talbot effect by a diffraction grating and Moire fringes in combination with another diffraction grating, i.e., X-ray Talbot interferometer has been studied as described, for example, in U.S. Pat. Nos. 5,812,629 and 7,180,979.
U.S. Pat. Nos. 5,812,629 and 7,180,979 propose X-ray imaging apparatuses that include an X-ray source, two diffraction gratings, and an X-ray image detector, and in each apparatus the two diffraction gratings and X-ray image detector are planar shaped.
For medical diagnostic applications, an X-ray source that radiates widely spreading beams is generally used. X-rays emitted by such an X-ray source can pass through the diffraction gratings at a center portion without any difficulty, but as X-ray incident on a portion other than the center portion, X-rays may be gradually absorbed and shielded by diffraction members. In this manner, It is difficult for X-rays emitted widely spread to pass through the diffraction gratings because the X-rays are incident from oblique directions. For example, Japanese Unexamined Patent Publication No. 2006-259264 proposes an amplitude modulation grating in which metal X-ray absorption members, each having a width of 2 to 10 μm and a thickness of 25 to 100 μm, are disposed at an equal interval of 2 to 10 μm. It can be thought that the use of such a diffraction grating may possibly cause the problem described above. Accordingly, large-size X-ray phase contrast imaging has been difficult to adopt practically in medical diagnostic applications.
Consequently, Japanese Unexamined Patent Publication No. 2007-206075 proposes an X-ray imaging apparatus structured such that a strip of the diffraction grating does not form a shadow in a beam path.
Japanese Unexamined Patent Publication No. 2007-203063 describes an X-ray imaging apparatus having a detection element formed of multiple vertically long detection strips parallel to the grating lines of the phase grating. The X-ray imaging apparatus like this may obtain a phase image by a single image acquisition and may reduce the number of image acquisition times. Japanese Unexamined Patent Publication No. 2007-203062 describes an X-ray imaging apparatus that obtains a phase contrast image in the same manner as in Japanese Unexamined Patent Publication No. 2007-203063 and includes scintillation strips.
Further, U.S. Patent Application Publication No. 20090092227 proposes a slot-scanning X-ray phase contrast imaging apparatus.
The X-ray imaging apparatuses described in Japanese Unexamined Patent Publication No. 2007-206075 and U.S. Patent Application Publication No. 20090092227 are apparatuses that obtain a phase contrast image using a fan beam or a cone beam, but there are various restrictions and preferable conditions in order to obtain a large-size view of X-ray phase image.
Where a detection element formed of multiple vertically long detection strips is provided as in Japanese Unexamined Patent Publication Nos. 2007-203063 and 2007-203062, it is possible to reduce the number of X-ray exposure times for obtaining a phase contrast image, but it is necessary to design the pitch between each detection strip much narrower. It is difficult to manufacture such narrower strips.
In view of the circumstances described above, it is an object of the present invention to provide a radiation phase contrast imaging apparatus capable of performing a large-size view of a radiation phase contrast imaging and being manufactured easily.